Methods and systems for hydrogen liquefaction
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Solution Overview
Problem
Current hydrogen liquefaction processes are energy-intensive and inefficient, with specific energy consumption (SEC) ranging from 6.7-12 kWh/kg liquid hydrogen and exergy efficiencies between 60-30%, limiting their operational cost-effectiveness and scalability.
Innovation Solution
The implementation of a system using twin expanders coupled in series with a N2/H2—Ne/H2/He Joule-Brayton refrigeration cycle, optimized for small and large-scale liquefiers, employing a single refrigerant or refrigerant mixture for closed-loop first and second stage refrigeration cycles, and utilizing nitrogen, neon, and helium as working fluids for pre-cooling and liquefaction, reducing the number of turbo machinery and operational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional hydrogen liquefaction processes are used, then hydrogen can be liquefied for storage and transport, but the specific energy consumption is high (6.7-12 kWh/kg LH2) and operational costs are high
Solution Approach 1:
The patent combines the pre-cooling cycle and liquefaction cycle into a single integrated system using a single refrigerant (nitrogen) for both stages. The refrigerant serves dual functions: first as a pre-cooling medium and then as the liquefaction refrigerant, eliminating the need for separate refrigerant systems and reducing overall energy consumption while lowering operational costs.
Solution Approach 2:
The nitrogen refrigerant performs multiple functions within the system: it acts as the working fluid for pre-cooling, then transitions to serve as the liquefaction refrigerant in the second stage. This multi-functionality reduces the complexity of the system and minimizes energy losses associated with multiple refrigerant circulation systems.
2Loss of energy
If multiple refrigerants and cascade cycles are used, then liquefaction efficiency can be improved, but the process complexity and capital costs increase significantly
Solution Approach 1:
The patent merges the pre-cooling and liquefaction cycles into one unified nitrogen-based refrigeration system. Instead of using separate refrigerants for each stage, the system uses nitrogen throughout, simplifying the process design and reducing capital costs while maintaining acceptable exergy efficiency through optimized heat exchanger configurations.
Solution Approach 2:
The patent extracts and eliminates the complex cascade refrigeration system with multiple refrigerants (hydrocarbon refrigerants, mixed refrigerants) from the design. By removing these unnecessary components and using a single nitrogen refrigerant system, the process complexity is significantly reduced while still achieving efficient hydrogen liquefaction.
3Ease of operation
If smaller liquefaction plants are designed, then simplicity and ease of operation are improved, but the scale and productivity are limited
Solution Approach 1:
The patent employs dynamic optimization of the nitrogen refrigeration system, using variable speed compressors and adjustable heat exchanger configurations to adapt the system's cooling capacity to match demand. This allows smaller plants to operate simply when needed while scaling up productivity during high-demand periods without requiring fundamentally different designs.
Solution Approach 2:
The refrigeration system is divided into modular sections (pre-cooling section and liquefaction section) that can be independently optimized and scaled. This segmentation allows the plant to maintain simplicity in each module while achieving high overall productivity through coordinated operation of the segmented system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves a significant reduction in SEC by 30-40%, lowering it to 5.2 kWh/kg LH2, thereby enabling economical large-scale production of liquid hydrogen with improved energy efficiency and reduced capital costs.
Implementation Method 1
flowing the gaseous hydrogen through a first refrigeration stage comprising a first refrigerant flowing through a first heat exchanger in a first refrigerant stream to cool the gaseous hydrogen
Implementation Method 2
flowing the cooled gaseous hydrogen through a second refrigeration stage comprising: flowing a second refrigerant in a second refrigerant stream through a second heat exchanger
Data Source
AI summary
Systems and methods for liquefying a gaseous hydrogen that include a first refrigeration stage and a second refrigeration stage. The first refrigeration stage includes a first heat exchanger configured to flow a first refrigerant to pre-cool the gaseous hydrogen. The second refrigeration stage includes a second heat exchanger configured to flow a second refrigerant to liquefy and sub-cool the hydrogen. The second refrigerant is split into two streams that flow through two compressor-expanders and multiple passes through the second heat exchanger before being recombined to repeat the second refrigeration stage circuit.